Though there are many forms of eye disease that can affect people, the end results are generally the same – sight gradually worsens and their quality of life is significantly affected.
As the population ages and develops more eye-related illnesses, pharmaceutical companies will need to develop new drugs that can overcome them, but this is only possible if there are ways of administering the treatments.
In many cases, there will be drugs that can only be administered by injecting into the eye with a hypodermic needle to target the condition exactly, and though tests show this is an effective means of getting to the root of the problem, the delivery of the drugs is a problem.
However, thanks to the development of new tiny microneedles, eye doctors may soon have a better way to treat diseases such as macular degeneration that affect tissues in the back of the eye.
For the first time, researchers from the Georgia Institute of Technology and Emory University have demonstrated how microneedles less than a millimeter in length can deliver drug molecules and particles directly to the eye.
In tests in animal models, the injection targeted the suprachoroidal space of the eye, which provides a natural passageway for drug injected across the sclera to flow along the eye's inner surface and subsequently into the back of the eye.
According to the specialist behind the study, the minimally-invasive technique could represent a significant improvement over conventional methods that inject drugs into the centre of the eye or use eyedrops, which have limited effectiveness in treating many diseases.
The research, which is published in the July issue of the journal Investigative Ophthalmology & Visual Science, was supported by the National Eye Institute and led by Samirkumar Patel, the paper's first author and a postdoctoral researcher at Georgia Tech when the research was conducted.
He explained that it could lead to a simple and safe procedure that offers doctors a better way to target drugs to specific locations in the eye.
"The design and simplicity of the microneedle device may make it more likely to be used in the clinic as a way to administer drug formulations into the suprachoroidal space that surrounds the eye," the expert added.
Mr Patel said the study also showed that the suprachoroidal space could accommodate a variety of drugs and microparticles, which could open the door for the use of timed-release drugs that could reduce the need for frequent injections to treat chronic eye diseases.
The suprachoroidal space is located between two important structures in the eye - the sclera and the choroid – with fluids injected into this space travelling circumferentially around the eye, flowing drug solutions directly over the choroid and adjacent retina, which are the targets for many drug compounds.
According to the study, injections of fluids containing molecules and particles into that space not only reach the targeted structures, but also remained there for extended time periods.
Equally important, the molecules and particles do not significantly reach the lens or front part of the eye, where side-effects from drugs can occur, explained Mark Prausnitz, a Regents professor in Georgia Tech's School of Chemical and Biomolecular Engineering.
"The study showed that if we inject non-degradable particles into the suprachoroidal space and wait as long as two months, the particles remain. That means there is no natural mechanism to remove the particles from the eye," he added.
"Knowing this, we can design biodegradable particles with drugs encapsulated in them that can slowly release those drugs over a period of time that we could control."
Further studies will now determine whether the procedure can be rolled out for human use, the experts noted.